Bioinspired 3D‐Printed NiTi Metamaterials With Bivalve‐Like Crossed‐Lamellar Structures

ABSTRACT Metamaterials demonstrate unique mechanical properties and functional performance owing to their distinctive topological spatial structures. In this study, by mimicking the natural Saxidomus purpuratus shell, bioinspired crossed‐lamellar architectures with interlamellar apex angles ranging from 60° to 150° were designed and fabricated in NiTi metamaterials by laser beam powder bed fusion (PBF‐LB). The microstructural characteristics, monotonic, and cyclic compressive properties, as well as deformation and damage behaviors of the metamaterials were systematically characterized. The metamaterials were revealed to display pronounced mechanical anisotropy, and demonstrate obvious viscoelastic hysteresis under cyclic compression. The mechanical properties are strongly dependent on both the loading direction and the apex angle, with diverse deformation and damage modes that are closely linked to the structural stability. Moreover, the bioinspired metamaterials demonstrate outstanding elastic recovery capability, achieving recovery ratios exceeding 80% upon compression to 10% strain along selected orientations, which surpasses those for other porous NiTi alloys with varying porosities reported in the literature. This is attributed to the intrinsic superelasticity of NiTi in synergy with the good elasticity and mechanical stability conferred by the crossed‐lamellar structure. This study provides valuable insights into the structural design, performance optimization, and potential applications of 3D‐printed metamaterials.